Boiler Training11 0

8/9/2019 Boiler Training11 0

http://slidepdf.com/reader/full/boiler-training11-0 1/73

1

TRAINING

Module: Boilers



2 2

Purpose

To provide training on Boilers



3 3

Contents

General description of Boilers

Types of Boilers

Basic Construction (Boiler Parts)

Air pollution control

Material tecnology

!perational "onitoring

!perational Maintenance #utdo$n Maintenance



4 4

Boiler

An Enclosed Pressure Vessel

Heat by Combustion of Fuel transferred

to water to generate steam

Process :

Evaporation

Steam volume

increase to 1!""

times from waterand produces

tremendous force

#oiler is an e$tremely

dangerous e%uipment&Care is must to avoid

e$plosion&



5 5

Heating surface is e$pressed in s%uare feet or in s%uare meter 1& 'adiant Heating Surfaces

(direct or primary)

*& Convective Heating Surfaces

(indirect or secondary)

+& E$tended Heating Surfaces

Various heating surfaces in a boiler

includes all water , bac-ed surfaces

t.at are directly e$posed to t.e radiant

.eat of t.e combustion flame&

includes all t.ose water/bac-ed surfaces

e$posed only to .ot combustion gases&

refers to t.e surface of

economi0ers and super .eaters used in

certain types of water tube boilers&



6 6

Typical Boiler Specification

Boiler Ma%e & 'ear : ' & *++,

MCR : -+TP. (/ & A -++0C)

(Ma1i"u" Continuous Rating)

Rated 2or%ingPressure : -+345 6G7CM*(G)

Type of Boiler : , Pass8 /ire tu9e8 pac%aged

/uel /ired : /uel !il

Total .eating #urface : ,-+ M*



7 7

Various heating surfaces in a boiler Typical Boiler SpecificationBoiler Systems

ater treatment system Feed water system

Steamsystem #lowdown

system

Fuel supply system Air supply system

Flue gas system



8 8

Fire in tube or Hot gas t.roug. tubes andboiler feed water in s.ell side

Fire 2ubes submerged in water

Boiler Types and classifications

ire Tube Boilers

!ater Tube Boilersater in tube or water passing t.roug. t.e

tubes and .ot gases passing outside t.e tubes

"ac#aged Boilers

Comes as a complete pac-ageand generally of s.ell type wit. fire tube design

so as to Ac.ieve .ig. .eat transfer rates by bot.radiation and convection



$ 9

%pplication

3sed for

small steam

capacities(3p to 1*"""

-g4.r and

156 -g4cm*)

&haracteristics o$ Capital Cost

/uel ;fficient

(<*=)

;asier to operate

Accepts $ide &

load fluctuations

#tea" pressure

variation is less

(arge volu"e of

$ater)

ire Tube Boilers



'( 10

%pplication7 3sed in Power

Plants

7 Steam capacities

range from 8&6

/1*" t4.r

&haracteristics7 .ig Capital Cost

> ?sed for igpressure ig capacity

stea" 9oiler

> @e"ands "ore

controls

> Calls for very

stringent $ater uality

!ater Tube Boiler



'' 11

2ater tu9e 9oiler

Steam

)rum

)o*ncomers

+isers

+efractory

lue ,as

!ater "anel

Super heater

&on-ection Ban#



'2 12

%pplication

3sed in smaller

applicationsre%uiring lower

capacity and lower

pressure levels

&haracteristics

7 Small

combustion spaceand .ig. .eat

release resulting

in faster

evaporation

7 Hig.er t.ermalefficiency levels

compared wit.

ot.er boilers

"ac#aged Boiler



'3 13

B!I;R PART#

PR;##?R; PART#

/?; /;;@ING & /IRING ;?IPM;NT#

/;;@ 2AT;R #'#T;M

A#. .AN@ING #'#T;M

2A#T; .;AT R;C!;R' #'#T;M

AIR P!?TI!N C!NTR! #'#T;M

C.IMN;'



'4 14

PR;##?R; PART#

B!I;R @R?M

/?RNANC; T?B;#

B!I;R C!N;CTI!N BAN6 #?P;R .;AT;R



'5 15

/?; /;;@ING & /IRING ;?IPM;NT#

/?; #T!RAG;

/?; /IT;R M;C.ANI#M

/?; C!N;'!R #'#T;M /?; /;;@ING M;C.ANI#M

C!MB?#TI!N C.AMB;R

C!MB?#TI!N AIR CIRC?IT



'6 16

A#. .AN@ING #'#T;M

A#. @I#C.ARG; #'#T;M

A#. C!N;'!R

A#. TR!;'



'7 17

/;;@ 2AT;R #'#T;M

2AT;R TR;ATM;NT #'#T;M

#T!RAG; TAN6

/;;@ 2AT;R P?MP



'8 18

2A#T; .;AT R;C!;R' #'#T;M

;C!N!MI#;R

AIR PR; D .;AT;R



'$ 19

AIR P!?TI!N C!NTR! #'#T;M

C'C!N;

#CR?BB;R

;#P BAG /IT;R



2( 20

Cyclone

It is also called a centrifugal separator3 It uses centrifugal force totro$ solids out of te fluid3 It is reco""ended as a solution tore"oving solids in te stuffing 9o1 tat could clog a "ecanical seal

and open te lapped faces3 It does not $or% very $ell in tese slurry applications3 To 9e really

effective tese units sould 9e used in a 9an% of several separators8connected in series3

Te nor"al installation is to ave iger pressure discarge fluidconnected to te side of te unit $it te 9otto" connected to tesuction side of te pu"p3 Te clean outlet8 on top8 is ten connectedto te stuffing 9o13



2' 21

Cyclone

Cyclones operate to collect relatively large siEe particulate "atterfro" a gaseous strea" troug te use of centrifugal forces3 @ustladen gas is "ade to rotate in a decreasing dia"eter pat$ay

forcing solids to te outer edge of te gas strea" for deposition intote 9otto" of te cyclone3 ;fficiencies of F+= in particle siEes of -+"icrons or greater are possi9le

Performance & Collection Efficiency inear increases $it: particle density8 gas strea" velocity8 and

rotational passes inear decrease $it fluid viscosity ;1ponential increase $it particle dia"eter



22 22

Cyclone



23 23

Cyclone





25 25

!pti"al flo$ rate difficult to adust and it is prone to internal erosion 7

corrosion

o$ efficiency for s"all dia"eter "aterial

.opper recirculation 7 flo$ distri9ution pro9le"s .ig energy costs for volu"etric flo$ reuire"ents

@e$ point agglo"eration8 9ridging8 and plugging

!ne of te li"itations in using tis unit in a centrifugal pu"p

application is tat often tere is very little pressure differential9et$een te stuffing 9o1 and te pu"p suction3 In so"e instances

tere is no differential at all3

Limitations





27 27

ABSORPTION & WET SCRUBBING EQUIPENT

Te goal in a9sorption and $et scru99ing euip"ent is te re"ovalof gases and particulate "atter fro" an e1aust strea" 9y causingte gaseous conta"ination to 9eco"e dissolved into te liuid

strea" and te solids to 9e entrained in te liuid3 Te rate of gas transfer into te liuid is dependent upon te

solu9ility8 "ass transfer "ecanis"8 and euili9riu" concentrationof te gas in solution3

Gas collection efficiencies in te range of FF= are possi9le3 Te

rate of particulate "atter collection at constant pressure drops isinversely proportional to te aerodyna"ic "ean dia"eter of teparticulate "atter and scru99er droplets3



28 28

#cru99er



2$ 29

2et #cru99er



3( 30

Performance & Efficiency Parameters

/or gas collection8 te "a1i"u" euili9riu" concentration in

solution is descri9ed 9y .enrys la$:

JCgasK L (.%) JCliuidK

$ereH

(.%) is .enrys constant

JCgasK is te concentration in te gas strea"

JCliuidK is te concentration in te liuid strea"



3' 31

Advantages

/e$ internal "oving parts

Reduced opportunity for gas ignition

Gas and liuid ce"istry control i"portant

Increased relative velocity 9et$een scru99ing te fluid and gas

strea"8 increases efficiency for solids



32 32

Limitations

.ig pressure drops reuired

Internal plugging8 corrosion8 erosion

Increased need for internal inspection

/or"ation 7 precipitation of solids



33 33

#cru99er Module



34 34

;#P

A precipitator is used to re"ove particulate (dust and soot) and prevent itfro" entering te at"ospere3

Te particulate is re"oved 9y passing a gas containing te particulate

past a series of ig voltage plates3 Te particulate is attracted to teseplates 9y te ig voltage static carge3 Rappers are used to %noc% te dust off te plates into te oppers 9elo$

for collection and disposal3 Te ig voltage static carge is produced 9ya transfor"er rectifier (T3R3)3 Tis ta%es A3C3 po$er fro" te facility8

9oosts te voltage and rectifies it to produce @3C3 Tis is used to cargete plates3 Te plates potential can 9e in e1cess of 4+8+++ volts3 /or tis reason8 access "ust 9e restricted until safe3 Te po$er "ust 9e

loc%ed off and te plates grounded to re"ove residual carges3



35 35

;#P Tis control device utiliEes gaseous ions to carge particles $ic are ten

"oved troug an electric field to 9e deposited onto carged collectionplates3

Collected particulate "aterial is ten re"oved 9y rapping or $asing of te

plates3 To produce te free ions and electric field8 ig internal voltages are reuired3 #ince te collection process does not rely on "ecanical processes suc as

sieving or i"paction8 9ut rater electrostatic forces8 te internal gas passages $itin a precipitator are relatively open $it s"all pressure drops and lo$er

energy costs to "ove te gas strea"3 .ig collection efficiencies are possi9le8 9ut collecting efficiency "ay

drastically cange $it canges in operating para"eters



36 36

;#P



37 37

;#P



38 38

;#P



3$ 39


Collection ;ff3 = L - D e D2A7B $ereH A L collecting electrode area

L volu"etric gas flo$ rate

2 L particle drift velocity and drift vel3 L 2 L;o ;p aC

(pi) $ereH

;o L carging field

;p L collecting field

a L particle radius C L proportionality constant

n L gas viscosity



4( 40

Limitations

arge installation space reuired

ReDentrain"ent8 spar%Dover8 9ac% corona pro9le"s

#uscepti9le to canges in "oisture and resistivity



4' 41

Advantages

.ig efficiencies for s"all particles possi9le

o$ pressure drops and air "oving costs

.ig potential for ignition sources

.ig te"perature operation possi9le





43 43

Bag .ouse7Bag /ilter

Bagouses utiliEe sieving8 i"paction8 agglo"eration8 and electrostaticfiltration principles to re"ove solids fro" a gaseous e1aust strea"3

Bagouses "a1i"iEe te filtration area 9y configuring te fa9ric filter

"edia into a series of long s"allDdia"eter fa9ric tu9es referred to as9ags3 Tey are tigtly pac%ed into a ousing $erein te dust laden air

"oves across te 9ag fa9ric tere9y re"oving it fro" te gas strea"and 9uilding up a filter ca%e $ic furter enances air cleaning3

Te filter ca%e is re"oved to oppers 9y various sa%ing "eans3 Teoperating pressure drop across te 9ags is descri9ed 9y:



44 44


Pressure drop L dP L #e 6C*t

$ereH #e L drag coefficient

L velocity

6 L filter ca%e coefficient

C L inlet dust concentration

t L Collection running ti"e



45 45

A!"anta#es

.ig collection efficiencies

Possi9le to ave varia9le flo$ rates



46 46

i"itation

Internal condensation 7 corrosion

!verDte"perature li"itations

Need for internal inspection 7 access

Plugging 7 sortDcircuiting 7 9rea%Dtroug7 collection "edia fouling

Accu"ulation of fla""a9le gases7 dusts and ignition sources

?ne1pected 9ag failure due to canges in operating para"eters



47 47

Bag /ilter



48 48

Bag /ilter



4$ 49

Bag filter



5( 50

Bag filter



5' 51

"erformance .-aluation of Boilers

Efficiency reduces wit. time due to7 Poor combustion7 Heat transfer fouling7 Poor operation and maintenance and7 9eterioration of fuel and water %uality

Factors for poor efficiency

Advantages of Efficiency testing

Helps us7 2o find out .ow far t.e boiler efficiency drifts away from t.e best

efficiency and7 2o target problem area for corrective action



7' 71

!perational Monitoring

Boiler Blo$ do$n

/eed $ater uality

#tea" uality

/uel7#tea" ratio

@ru" $ater

Te"perature

@rafts Pressure

?n9urnts





73 73

0ntermittent Blo* )o*n

7;ntermittent blown down is given by manually operating

a valve fitted to disc.arge pipe at t.e lowest point of

boiler s.ell to reduce parameters (29S or conductivity

pH Silica etc) wit.in prescribed limits so t.at steam%uality is not li-ely to be affected&

729S level -eeps varying

7Fluctuations of t.e water level in t.e boiler 7Substantial amount of .eat energy is lost wit.

intermittent blowdown&



74 74

&ontinuous Blo* )o*n

A Steady and constant dispatc. of small stream of concentrated

boiler water and replacement by steady and constant inflow of

feed water&

Ensures constant 29S and steam purity& <nce blow down valve is set for a given conditions t.ere is no

need for regular operator intervention& Even t.oug. large %uantities of .eat are wasted opportunity

e$its for recovering t.is .eat by blowing into a flas. tan- and

generating flas. steam& 2.is type of blow down is common in .ig. pressure boilers&

Bl ) . ti ti



75 75

Blo* )o*n1 .stimation

The uantity of Blo* do*n reuired to control boiler *ater solids concentration

continuous Blo* do*n is calculated by using the follo*ing formula

#lowdown = > 29S in F $ 1"" > (1"" 4 +8"") $ 1""

Allowable 29S in #oiler drum , 29S in F

#low down flow rate > += $ 1""""-g4.r > +""-g4.r

29S(C)> +6"" ppm

Allowable

Steam 1" 24.r

29S(2)>"

#low down (#)

29S(S) in feed water

1"" ppm





B il t t t t



78 78

Boiler *ater treatment

Boiler *ater treatment reuired to&ontrol steam purity

&ontrol deposits

control corrosion

%t ele-ated temp = "ressureSoluble components

in feed *ater

"articulate solidsSome times in crystalli:ed forms

and other times as

amorphous particles

Solubility of a specific

&omponent in *ater .<ceeds certain limit )e-elopment of

Scale or deposits

+ecommended feed ater limits



7$ 79

+ecommended feed *ater limits

+ecommended Boiler *ater limits



8( 80

+ecommended Boiler *ater limits



8' 81

+educe Stac# Temperature

7Stac- temperatures greater t.an *""?C indicates potential for

recovery of waste .eat&

7

;t also indicate t.e scaling of .eat transfer 4 recoverye%uipment and .ence t.e urgency of ta-ing an early s.ut down

for water 4 flue side cleaning&

**? C reduction in flue gas temperatureincreases boiler efficiency by 1=




82 82


eed !ater "reheating using .conomiser

For an older s.ell boiler wit. a flue gas e$it temperature

of *!"?C an economi0er could be used to reduce it to

*""?C ;ncrease in overall t.ermal efficiency would be in

t.e order of +=&

!?C raise in feed water temperature by

economi0er 4 condensate recovery correspondsto a 1= saving in fuel consumption&

+ d St # T t



83 83


;n order to improve t.ermal

efficiency by 1= t.e combustion air

temperature must be raised by *"?C&

&ombustion %ir "reheating

7Combustion air pre.eating is an alternative to feed

water .eating&



84 84

0ncomplete &ombustion& & & & & > &? &? &? &?

;ncomplete combustion can arise from a s.ortage of air or surplus of

fuel or poor distribution of fuel&

0n the case of oil and gas fired systems; &o or smo-e wit. normal

or .ig. e$cess air indicates burner system problems&E$ample : Poor mi$ing of fuel and air at t.e burner& Poor oil fires can

result from improper viscosity worn tips carboni0ation on tips and

deterioration of diffusers&

!ith coal firing oss occurs as grit carry/over or carbon/in/as. (*=

loss)&

E$ample : ;n c.ain grate sto-ers large lumps will not burn out

completely w.ile small pieces and fines may bloc- t.e air passage

t.us causing poor air distribution&

;ncrease in t.e fines in pulveri0ed coal also increases carbon loss&

&ontrol e<cess air



85 85

&ontrol e<cess air

2.e optimum e$cess air level varies wit. furnace design type of burner

fuel and process variables&

0nstall o<ygen trim systemor e-ery '@ reduction in e<cess air; (96@ rise in efficiency9



86 86

+adiation and &on-ection eat Aoss

72.e surfaces lose .eat to t.e surroundings depending on t.e

surface area and t.e difference in temperature between t.e

surface and t.e surroundings&

72.e .eat loss from t.e boiler s.ell is normally a fi$ed energy

loss irrespective of t.e boiler output& it. modern boiler

designs t.is may represent only 1&6= on t.e gross calorific

value at full rating but will increase to around != if t.e boiler

operates at only *6 percent output&

7'epairing or augmenting insulation can reduce .eat loss

t.roug. boiler walls&



87 87

+eduction of Scaling and Soot Aosses

7;n oil and coal/fired boilers soot buildup on tubes acts as an insulator

against .eat transfer& Any suc. deposits s.ould be removed on a

regular basis& Elevated stac- temperatures may indicate e$cessive soot

buildup& Also same result will occur due to scaling on t.e water side&

7Hig. e$it gas temperatures at normal e$cess air indicate poor .eat

transfer performance& 2.is condition can result from a gradual build/up

of gas/side or waterside deposits& aterside deposits re%uire a review

of water treatment procedures and tube cleaning to remove deposits&

7Stac- temperature s.ould be c.ec-ed and recorded regularly as an

indicator of soot deposits& .en t.e flue gas temperature rises about

*"?C above t.e temperature for a newly cleaned boiler it is time to

remove t.e soot deposits&



88 88

+eduction of Scaling and Soot Aosses

7;ncorrect water treatment poor combustion and poor

cleaning sc.edules can easily reduce overall t.ermal

efficiency&

7However t.e additional cost of maintenance and cleaningmust be ta-en into consideration w.en assessing savings&

.-ery millimeter thic#ness ofsoot coating increases the stac#

temperature by about 55&9

3 mm of soot can cause an

increase in fuel consumption

by 295@9

% 'mm thic# scale

deposit on the *aterside could increase

fuel consumption

by 5 to 8@9

+eduction of Boiler Steam "ressure



8$ 89

%d-erse effects; such as

an increase in *ater carryo-er

from the boiler o*ing to

pressure reduction;

may negate any

potential sa-ings9

"ressure should bereduced in stages;

and no more than a

2( percent reduction

should be considered9

+eduction of Boiler Steam "ressure

7 ower steam pressure gives a lower saturated steam temperature and

wit.out stac- .eat recovery a similar reduction in t.e temperature of

t.e flue gas temperature results& Potential 1 to *= improvement&

7 Steam is generated at pressures normally directed by t.e .ig.estpressure 4 temperature re%uirements for a particular process& ;n some

cases t.e process does not operate all t.e time and t.ere are periods

w.en t.e boiler pressure could be reduced&





$' 91

!perational Maintenance and #utdo$n Maintenance

Cec%ing of Pressure parts for

#agging

@istortion

Tic%ness

Refractories7Insulation

/ans7Pu"ps

@ucting #tea" dru"

Boiler +eplacement



Te feasi9ility study sould e1a"ine all

I"plications of long ter" fuel availa9ility

and co"pany gro$t plans3 All financial and engineering

factors sould 9e considered3 #ince 9oiler plants

traditionally ave a useful life of $ell over *4 years8

replace"ent "ust 9e carefully studied3

Boiler +eplacement

If te e1isting 9oiler is :

!ld and inefficient8 not capa9le of firing ceaper su9stitution fuel8 over or

underDsiEed for present reuire"ents8 not designed for ideal loading

conditions replace"ent option sould 9e e1plored&

Date post:	01-Jun-2018
Category:	Documents
Upload:	anoop-prajapati
View:	220 times
Download:	0 times

Boiler Training11 0

Documents